Large Plastic Deformation and Ultra-Fine Grained Structures Generated by Machining

2008 ◽  
Vol 375-376 ◽  
pp. 21-25 ◽  
Author(s):  
Wen Jun Deng ◽  
Wei Xia ◽  
Yong Li ◽  
Zhen Ping Wan ◽  
Yong Tang
Keyword(s):  
Plastic Deformation ◽  
Element Model ◽  
Machining Process ◽  
Machining Parameters ◽  
Large Plastic Deformation ◽  
Low Velocity ◽  
Fine Grained ◽  
Orthogonal Machining ◽  
Transmission Electron ◽  
Quantitative Understanding

Microstructure of machined copper chips at very low velocity was characterized by transmission electron microscopy. The structure of the machined chip produced by reasonable combinations of machining parameters is virtually entirely occupied by isolated equiaxed submicron grains of 100~300nm in size with high-angle boundaries. A finite element model was developed to study large plastic deformation in plain orthogonal machining copper. The numerical results show most of the grain refinement associated with the formation of ultra-fine grained chip may be attributed to the large shear strain imposed in the deformation zone. It is feasible to take machining process as a method of preparing ultra-fine grained materials. But the optimal design of the machining process requires a precise and quantitative understanding of the mechanics of deformation-induced subgrain microstructure.

Effect of Severe Plastic Deformation in Machining Elucidated via Rate-Strain-Microstructure Mappings

2012 ◽  
Vol 134 (3) ◽  
Author(s):  
S. Shekhar ◽  
S. Abolghasem ◽  
S. Basu ◽  
J. Cai ◽  
M. R. Shankar
Keyword(s):  
Plastic Deformation ◽  
Severe Plastic Deformation ◽  
Strain Rate ◽  
Deformation Zone ◽  
Fine Grained ◽  
Orthogonal Machining ◽  
Deformation Parameters ◽  
Strain And Strain Rate ◽  
One To One ◽  
Surface Microstructures

Machining induces severe plastic deformation (SPD) in the chip and on the surface to stimulate dramatic microstructural transformations which can often result in a manufactured component with a fine-grained surface. The aim of this paper is to study the one-to-one mappings between the thermomechanics of deformation during chip formation and an array of resulting microstructural characteristics in terms of central deformation parameters–strain, strain-rate, temperature, and the corresponding Zener–Hollomon (ZH) parameter. Here, we propose a generalizable rate-strain-microstructure (RSM) framework for relating the deformation parameters to the resulting deformed grain size and interface characteristics. We utilize Oxley’s model to calculate the strain and strain-rate for a given orthogonal machining condition which was also validated using digital imaging correlation-based deformation field characterization. Complementary infrared thermography in combination with a modified-Oxley’s analysis was utilized to characterize the temperature in the deformation zone where the SPD at high strain-rates is imposed. These characterizations were utilized to delineate a suitable RSM phase-space composed of the strain as one axis and the ZH parameter as the other. Distinctive one-to-one mappings of various microstructures corresponding to an array of grain sizes and grain boundary distributions onto unique subspaces of this RSM space are shown. Building on the realization that the microstructure on machined surfaces is closely related to the chip microstructure derived from the primary deformation zone, this elucidation is expected to offer a reliable approach for controlling surface microstructures from orthogonal machining.

Charged-Particle Emissions During Material Deformation, Failure and Tribological Interactions of Machining

2018 ◽  
Vol 141 (3) ◽  
Author(s):  
Jagadeesh Govindaraj ◽  
Sathyan Subbiah
Keyword(s):  
Plastic Deformation ◽  
Charged Particle ◽  
Emission Intensity ◽  
Cutting Tool ◽  
Charged Particles ◽  
Machining Process ◽  
Work Piece ◽  
Machining Parameters ◽  
Particle Emissions ◽  
Faraday Plate

Charged particles are emitted when materials undergo tribological interactions, plastic deformation, and failure. In machining, plastic deformation and shearing of work piece material takes place continuously along with intense tool-chip rubbing contact interactions; hence, the emission of charged particles can be expected. In this work, an in-situ sensor has been developed to capture the emitted positive (positive ion) and negative (electron and negative ion) charged particles in real-time in an orthogonal machining process at atmospheric conditions without the use of coolant. The sensor consists of a Faraday plate, mounted on the flank face of the cutting tool, to collect the emitted ions and the intensity of emissions is measured with an electrometer. Positively and negatively charged particles are measured separately by providing suitable bias voltage supply to the Faraday plate. Ion emissions are measured during machining of three different work piece materials (mild steel, copper, and stainless steel) using a carbide cutting tool. The experimental results show a strong correlation between the emission intensity and the variation in machining parameters and material properties. Increasing material removal rate increases the intensity of charged particle emissions because of the increase in volume of material undergoing shear, fracture, and deformation. It is found that emission intensity is directly proportional to the resistivity and strength of workpiece material. Charged particles emission intensity is found to be sensitive to the machining conditions which enables the use of this sensor as an alternate method of condition monitoring.

The surface integrity of ultra-fine grain steel, Electrical discharge machined using Iso-pulse and resistance–capacitance-type generator

2020 ◽  
Vol 234 (4) ◽  
pp. 564-573
Author(s):  
Mohammad S Mahdieh
Keyword(s):  
Surface Integrity ◽  
Electrical Discharge ◽  
Electrical Discharge Machining ◽  
High Strength ◽  
Functional Method ◽  
Machining Process ◽  
Machining Parameters ◽  
Fine Grained ◽  
Hardness Tester ◽  
Angular Pressing

Ultra-fine grained materials with high strength and low weight are eventually considered to be used in industries. To produce ultra-fine grained materials, equal channel angular pressing is a functional method, imposing severe plastic deformation on the workpiece. Electrical discharge machining is an indispensable process in manufacturing industrial parts with high accuracy and precision. However, electrical discharge machining has thermo-physical consequences, damaging the surface layers of the workpiece. On the other hand, the ultra-fine grained materials are thermodynamically unstable and tend to microstructural evolution. Thus, electrical discharge machining process affects the ultra-fine grained materials more than coarse grain materials. In this study, the effects of electrical discharge machining on the ultra-fine grained steel were investigated and the undesirable influences of the electrical discharge machining were diminished by adjusting the electrical discharge machining parameters. The ultra-fine grained steel samples were electrical discharge machined in two methods including Iso-pulse (roughing mode and finishing mode) and with resistance–capacitance-type generator. The surface integrity parameters, including thickness and microstructure of the recast layer and heat-affected zone, the cracks density and hardness, which for all three types of samples, were investigated by scanning electron microscopy, optical microscopy, X-ray diffraction technique, and micro-hardness tester. The results show that electrical discharge machining with resistance–capacitance-type generator has the minimum effects on the surface integrity of the ultra-fine grained samples because of the different material removal mechanism of resistance–capacitance-type electrical discharge machining.

Comparison Orthogonal Tube Turning Data Versus Finite Element Simulation Using LS Dyna

2013 ◽  
Author(s):  
Vishnu Vardhan Chandrasekaran ◽  
Lewis N. Payton
Keyword(s):  
Finite Element ◽  
Metal Cutting ◽  
Tool Material ◽  
Element Model ◽  
Rake Angle ◽  
Machining Process ◽  
Work Piece ◽  
Orthogonal Machining ◽  
Work Material ◽  
Cut Depth

The current study focuses on building a 2-Dimensional finite element model to simulate the orthogonal machining process under a dry machining environment in a commercially available FEA solver LS DYNA. One of the key objectives of this thesis is to carefully document the use of LS Dyna to model metal cutting, allowing other researchers to more quickly build on this work. Actual force data is obtained using an Orthogonal Tube Turning apparatus that has been statistically validated to an accuracy of 99+%. The work material used in this study is Aluminum 6061-T6 alloy. The tool material is tool steel, which is modeled as a rigid body. A Plastic Kinematic Material Hardening model is used to define the work material. Chip formation is based on the effective failure plastic strain. A constant coefficient of friction between the tool and work piece is used, obtained from the actual experimental results. The simulation is carried out with the same constant velocity, different rake angles and depth cuts as in the real world experiment. The cutting force and thrust force values obtained for each combination of rake angle and cut depth are validated against the experimental data obtained at Auburn University. The resulting model is considered valid enough to use for sensitivity analysis of the metal cutting process in aluminum alloy 6061-T6 in the university environment. The model is available publicly to any university from a website provided.

Nano-Structuring of 316L Type Steel by Severe Plastic Deformation Processing Using Two-Dimensional Linear Plane Strain Machining

2014 ◽  
Vol 783-786 ◽  
pp. 2720-2725 ◽  
Author(s):  
Jorg M.K. Wiezorek ◽  
G. Facco ◽  
Y. Idell ◽  
A. Kulovits ◽  
M.R. Shankar
Keyword(s):  
Plastic Deformation ◽  
Plane Strain ◽  
Magnetic Measurements ◽  
Severe Plastic Deformation Processing ◽  
X Ray Diffraction ◽  
Deformation Processing ◽  
Fine Grained ◽  
Transmission Electron ◽  
Strain Induced Martensite ◽  
Property Changes

Using a novel plastic deformation technique, termed linear plane-strain machining, large shear strains up to ~2.3 have been imparted to 316L stainless steel at rates of up to 1700/s. Combinations of hardness and magnetic measurements, X-ray diffraction (XRD) and transmission electron microscopy (TEM) experiments were used to monitor the microstructural and mechanical property changes for the room temperature plastic deformation processing. Grain refinements to the ultra-fine grained and even the nanocrystalline size regime have been achieved without formation of significant volume fractions of strain-induced martensite. The mechanical strength enhancements in the linear plane-strain machined 316L have been attributed to grain refinement and stored strain. The suppression of martensite formation has been correlated to significant adiabatic heating of the 316L during high strain rate plastic deformation processing.

Analysis of the Machining Process Using a Thermo-Elastic-Viscoplastic Finite Element Model

Manufacturing ◽  
2002 ◽  
Author(s):  
N. Balihodzic ◽  
H. A. Kishawy ◽  
R. J. Rogers
Keyword(s):  
Finite Element ◽  
Finite Element Model ◽  
Element Model ◽  
Machining Process ◽  
Tool Geometry ◽  
304L Stainless Steel ◽  
Stress Distributions ◽  
Temperature Dependent ◽  
Machined Surface ◽  
Orthogonal Machining

A plane-strain thermo-elasto-viscoplastic finite element model has been developed and used to simulate orthogonal machining. Simulations of cutting 304L stainless steel have been carried out using sharp, chamfered, and honed ceramic tools. Employing a combined thermal and mechanical stress analysis with temperature-dependent physical properties, the finite element model is used to investigate the effect of process parameters, tool geometry and edge preparation on the machining process. Stress and strain distributions within the chip and the elastic tool are presented. In addition, trends in the cutting and thrust forces, contact stress distributions and the plastic deformation beneath the machined surface are studied.

Experimental Investigation of Charged Particles Emission in Machining: Towards Process Monitoring

2018 ◽  
Author(s):  
Jagadeesh Govindaraj ◽  
Sathyan Subbiah
Keyword(s):  
Plastic Deformation ◽  
Emission Intensity ◽  
Cutting Tool ◽  
Shear Fracture ◽  
Charged Particles ◽  
Machining Process ◽  
Negative Ion ◽  
Work Piece ◽  
Machining Parameters ◽  
Faraday Plate

Charged particles are emitted when a material undergoes plastic deformation and failure. In machining, plastic deformation and shearing of work piece material takes place continuously; hence, emission of charged particles can be expected. In this work, an in-situ sensor has been developed to capture the emitted positively (positive ion) and negatively (electron and negative ion) charged particles in real time in an orthogonal machining process at atmospheric conditions without the use of coolant. The sensor consists of a Faraday plate, mounted on the flank face of the cutting tool, to collect the emitted ions and the intensity of emissions is measured with an electrometer. Positively and negatively charged particles are measured separately by providing suitable bias voltage supply to the Faraday plate. Ion emissions are measured during machining of three different work piece materials (mild steel, copper and stainless steel) using a carbide cutting tool. The experimental results show a strong correlation between the emission intensity and variation in machining parameters and material properties. Increasing material removal rate in machining increases the intensity of charged particle emissions because of increase in volume of material undergoing shear, fracture, and deformation. It is found that emission intensity is directly proportional to the resistivity and strength of workpiece material. Charged particles emission intensity is found to be very sensitive to the machining conditions which enables the use of this sensor as an alternate method of tool condition monitoring.

Recast layer and micro-cracks in electrical discharge machining of ultra-fine-grained aluminum

2016 ◽  
Vol 232 (3) ◽  
pp. 428-437 ◽  
Author(s):  
Mohammad Sajjad Mahdieh ◽  
RamezanAli Mahdavinejad
Keyword(s):  
Plastic Deformation ◽  
Heat Affected Zone ◽  
Electrical Discharge ◽  
Electrical Discharge Machining ◽  
Recast Layer ◽  
Machining Process ◽  
Coarse Grain ◽  
Fine Grained ◽  
Micro Cracks ◽  
Sever Plastic Deformation

Aluminum alloys, due to lightweight, are widely used in aerospace and automotive industries. However, the low strength of aluminum has hindered its application. The strength of aluminum can be improved in many ways. One of them is decreasing the average grain size of metal by applying sever plastic deformation methods. Equal channel angular pressing is the most functional technique of sever plastic deformation producing ultra-fine-grained metals. Using post-process methods such as electrical discharge machining to manufacture industrial parts of ultra-fine-grained material is very conventional. The recast layer which is the consequence of electrical discharge machining process may cause undesirable influence on the surface of ultra-fine-grained aluminum. In this article, the recast layer and the heat-affected zone of electrical discharge machining of ultra-fine-grained aluminum are investigated. The thickness of recast layer, heat-affected zone and micro-cracks is observed using scanning electron microscopy and optical microscopy. In addition, the phase composition and the hardness of the recast layer and heat-affected zone are investigated by applying X-ray diffraction technique and micro-hardness test. These experiments are also repeated for the coarse-grain aluminum, and the results are compared with ultra-fine-grained aluminum. Results show that the electrical discharge machining deteriorates the surface integrity of the ultra-fine-grained aluminum rather than coarse-grain aluminum.

Deformation Replication

1970 ◽  
Vol 28 ◽  
pp. 280-281
Author(s):  
J. Temple Black
Keyword(s):  
Cutting Speed ◽  
Machining Process ◽  
Depth Of Cut ◽  
Rake Face ◽  
Orthogonal Machining ◽  
Aluminum Chips ◽  
Before And After ◽  
Materials Used ◽  
Glass Knife ◽  
Very High

Tool materials used in ultramicrotomy are glass, developed by Latta and Hartmann (1) and diamond, introduced by Fernandez-Moran (2). While diamonds produce more good sections per knife edge than glass, they are expensive; require careful mounting and handling; and are time consuming to clean before and after usage, purchase from vendors (3-6 months waiting time), and regrind. Glass offers an easily accessible, inexpensive material ($0.04 per knife) with very high compressive strength (3) that can be employed in microtomy of metals (4) as well as biological materials. When the orthogonal machining process is being studied, glass offers additional advantages. Sections of metal or plastic can be dried down on the rake face, coated with Au-Pd, and examined directly in the SEM with no additional handling (5). Figure 1 shows aluminum chips microtomed with a 75° glass knife at a cutting speed of 1 mm/sec with a depth of cut of 1000 Å lying on the rake face of the knife.

Sign in / Sign up

Export Citation Format

Share Document